Metallic bond in transition metals

Metal-metal bonds in transition metal compounds. M. C. Baird, Prog. Inorg. Chem., 1968,9,1-159 (899). 

Metal-metal bonds in transition metal complexes 16... 

Baird, Michael C., Metal-Metal Bonds in Transition Metal Compounds. 9 1... 

Metal-metal bonding in transition metal complexes of low nuclearity (i.e., with only a few metal atoms) tends to be more directed and therefore stronger than the bonding in metals discussed in chapter 11. Accordingly, the metal-metal bonds in transition metal complexes are often localized and considerably shorter than those in most extended solids. Charge accumulations are frequently observed in metal-metal bonding regions of deformation density maps. 

The prediction of metal-to-metal bonding in transition metal binary and related compounds. Australian J. Chem. 17, 1191 (1964). 

Current interest in metal cluster compounds has arisen from the demonstration that metal-metal bonds play a key role in determining the chemistry of large classes of compounds, in particular, those with heavy metal atoms in low valent states. The occurrence of metal-metal bonding in transition metal complexes has been surveyed 21, 26, 59, 271, 275), and the criteria for metal-metal bonding and the factors contributing to the stability of such bonds have been discussed. Schafer and Schnering Sll) and more recently Keppert and Vrieze 229) have reviewed the lower halide, oxide, and oxyhalide clusters of the heavier transition metals. Cotton 102) has considered the transition metal clusters in terms of structural types, and a similar approach has been adopted in a review of molecular polyhedra of high coordination number 309). 

This ion was one of the prototypes of multiple bonding between two transition-metal ions. It was discovered and characterized in 1965 by Cotton and Harris. The Re—Re bond distance was determined to be only 2.24 A, and it was concluded that it is a quadruple bond. A similar short bond had earlier been found in the trinuclear complex [Re3Cli2] . These ions were to form the conceptual basis for the forthcoming development of the field multiple metal-metal bonding in transition-metal chemistry. 

Metal—metal bonds in transition metal carbonyls can be cleaved by halogens. Mn lCO), affords the complexes XMn(CO)5, (X = Cl Br, I) (cf. Os3(CO)i2 p, 352). Halogens also attack metal carbonyls which do not possess M—M bonds with loss of carbonyl ligands e.g. 

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